I just noticed that Joel was talking about personal sites configuration and I realized that I never posted about my experience upgrading customers way back in the day. I bet some of you are experiencing this or will be experiencing this in the future so let me save you some trouble. Yes, it's possible to host sites and personal sites in the same web app and you can even view the public profile properties on the same web app if you configure it correctly. It's been almost a year since I did this so bear with me. First, you really do need a mysite host to see public profiles in 2007. Without it you won't see profile information and search won't be able to index the profiles either. Additionally, the timer jobs that ensure your WSS user information is synced with the profile database wont work.
You get the impression when trying to configure a mysite host that it has to be the top level site in a standalone web app. However, you can create one anywhere in your site hierarchy. You do this by using STSADM to create a web with mysite host template. (stsadm-o createweb -url http://site/mysitehostname -sitetemplate SPSMSITEHOST) If you have a portal at http://site, it makes sense to put your mysite host at http://site/my. No one browses this particular web as it's set to redirect users to their personal site. By default, any web created within a collab portal will be exposed on the site navigation menu. This is an easy fix as you can choose to hide the web in the site's navigation properties.
Update: Bill Baer actually posted about this back in February although he muddied up the topic with some upgrade stuff as well 😉 Here's the link: http://blogs.technet.com/wbaer/archive/2007/02/19/co-hosting-team-and-personal-site-collections-within-an-individual-web-application.aspx